The present invention relates generally to a fuel supply system and carburetor for a motor vehicle, and more particularly, to the needle valve assembly typically used within the carburetor at the fuel inlet port.
A basic fuel supply system for a motor vehicle includes a fuel tank, and a fuel pump which carries fuel along a fuel line through the pump and directs the fuel into a carburetor. There, it is mixed with air for subsequent combustion within the engine.
One variation on this design, provided as a means of reducing emissions from the engine, includes a fuel return line extending from the fuel pump outlet back to the tank. A check valve is provided within this line near the tank to prevent unwanted flow of fuel from the tank toward the carburetor or out of the fuel tank in the event of an accident.
At the fuel inlet to the carburetor, a needle valve is disposed for cooperation with the fuel float assembly inside the carburetor. The valve is disposed within a seat and is normally pushed to an open position by the flow of fuel into the carburetor. The rear of the needle valve is in contact with a pivotally mounted float assembly, so that as the float chamber fills with fuel, the needle valve is pushed back into its seat, thereby reducing fuel flow.
A problem which has been exhibited by some vehicles having a fuel system of this type appears after the vehicle has been operated and then shut down for some period of time. After such time, the engine cannot be restarted or, if some fuel remains within the carburetor, the engine starts long enough to use this fuel and then stops. This problem is intermittent, and thus its occurrence is impossible to predict. Further, it does not seem to affect all vehicles of a similar type.
The inability to start the engine appears to be caused by the needle valve becoming firmly stuck within its seat to the extent that fuel pressure from the fuel pump is insufficient to open the valve. Occasionally, replacement of the needle valve and seat assembly seems to cure or reduce the problem. In other instances, replacement of this assembly seems to have no effect.
What is needed therefore, is a solution to the problem of sticking of the needle valve. Of course, such a solution should be effective, but moreover, should be easily carried out and involve relatively little cost in view of the potentially large number of vehicles affected.